Designs and Prospects of Bi-2212 Canted-Cosine-Theta Magnets to Increase the Magnetic Field of Accelerator Dipoles Beyond 15 T

REBa 2 Cu 3 O x (REBCO, RE = rare earth elements) coated conductors can carry high current in high background fields, in principle enabling dipole magnetic fields beyond 20 T. Although model accelerator magnets wound with single REBCO tapes have been successfully demonstrated, magnet technology based on high-current REBCO cables for high-field accelerator magnet applications has yet to be established. We developed a two-layer canted cos θ dipole magnet with an aperture of 70 mm using 30 m long commercial Conductor on Round Core (CORC R) wires. The 3.1 mm diameter CORC R wire contained 16 commercial REBCO tapes with a 30-µm thick substrate. The magnet was tested at 77 and 4.2 K. It generated a peak dipole field of 1.2 T with 4.8 kA at 4.2 K with neither thermal runaway nor training. Reasonable geometric field quality and strong magnetization-current effects with multipole decay were observed. Our work demonstrated a feasible high-temperature superconducting magnet technology as a first step toward a new accelerator magnet paradigm that will enable high-field inserts for next-generation circular colliders and stand-alone magnets that can operate over a wide temperature range for a broad range of applications.

Section: Magnet Designmentioning

confidence: 99%

A 1.2 T canted cosθ dipole magnet using high-temperature superconducting CORC^® wires

Wang

Dietderich

DiMarco

et al. 2019

“…To improve the preparation technology of Bi2212 wires with high J c , researchers need a high temperature and overpressure furnace of at least 50-100 bar. Bi2212 magnets generally need to be prepared by winding first and then PMR-HT [3,9,11]. Therefore, to conduct the research on Bi2212 magnet preparation technology, researchers need to have a large 50-100 bar high temperature and overpressure furnace.…”

Section: Introductionmentioning

confidence: 99%

Doubled J _c of Bi₂Sr₂CaCu₂O _x wires by partial melting and recrystallization heat treatment under 10 bar after vacuum degassing of the precursor powder and pre-densifying of the wires

Hao¹,

Li²,

Xu³

et al. 2021

Final heat treatment involving partial melting and recrystallization under a high pressure of 50–100 bar is not conducive to the preparation of Bi2Sr2CaCu2O x (Bi2212) magnets; it also greatly increases the cost of research into Bi2212 wires. To solve these problems, in this work a final heat treatment under 10 bar was used to prepare Bi2212 wires with a high bulk density and high critical current density (J c). The ambient pressure of the final heat treatment in this paper is only one-fifth of that of the traditional overpressure for final heat treatment of Bi2212 wires. The J c of the wires is more than 2.4 times higher than that of Bi2212 wires with a final heat treatment at 1 bar and is consistent with that of samples having a final heat treatment at the traditional 50–100 bar. The reason why the ambient pressure of the final heat treatment can be greatly reduced in this work is: (a) vacuum degassing of the precursor powder eliminated the adsorption and interstitial impurity gases in the long Bi2212 wires, and reduced the internal gas pressure of the wires; (b) pre-treatment at 800 °C and 250 bar compressed the Bi2212 wires to their full density. Thus, during the subsequent final heat treatment, the low ambient pressure of 10 bar can overcome the difference between the residual gas pressure inside the wires and the yield strength or creep strength of the Ag sheath, and prevent expansion of the internal gas in the wires, so that the Bi2212 wires are always close to full density. The ambient pressure of the final heat treatment in this paper needs to prevent the expansion of the Bi2212 wires not compress them, so the pressure can be very low. The 10 bar low pressure final heat treatment will solve the problems of the high cost of research into Bi2212 wires and the difficult overpressure heat treatment of Bi2212 magnets.

“…Such magnets would allow particle accelerators to operate at much higher beam energies, or compact fusion magnets to contain demountable joints, something that is beyond the capabilities of magnets wound from low-temperature superconductors (LTS). Several HTS materials are being developed into practical high-field magnet conductors, including Bi 2 Sr 2 CaCu 2 O x (Bi-2212) wires [1,2], Bi 2 Sr 2 Ca 2 Cu 3 O x (Bi-2223) tapes [3,4] and RE-Ba 2 Cu 3 O 7−δ (REBCO) coated conductors [5][6][7], where RE refers to various rare earth elements. One of the key remaining challenges with operating HTS magnets is to detect an incipient magnet quench.…”

Section: Introductionmentioning

confidence: 99%

CORC^® wires containing integrated optical fibers for temperature and strain monitoring and voltage wires for reliable quench detection

Laan

Weiss

Scurti

et al. 2020

Safe operation of large superconducting magnets wound from high-temperature superconductors (HTS) requires reliable detection of the onset of a quench. A novel method to integrate optical fibers and voltage wires within the core of multi-tape HTS CORC ® wires has been developed that allows real time monitoring of local changes in strain, temperature and of the superconducting state of the magnet windings. The ability to detect highly localized changes in temperature with Rayleigh scattering in the embedded optical fibers provides invaluable information about local heating at hot spots from which a quench may originate. Integrated voltage contacts allow accurate voltage measurements in long CORC ® wires without being affected by high current ramp rates or electromagnetic interference. They also allow detection of inductively driven redistribution of current between tapes in CORC ® wires that may occur at high current ramp rates. Continuous monitoring of temperature and voltage was used to detect the formation of local hot spots induced by a heater or by operating the CORC ® wire above its critical current. The results show that, within the boundary conditions of the experiment and the method by which the optical fibers were integrated into the CORC ® wire in this study, the speed and resolution with which hot spots can be detected with optical fibers lagged that of the integrated voltage wires. This study also shows that integrated voltage wires reliably detected the formation of a local hot spot in a 5.1 meter long coiled CORC ® wire, down to a hot spot size covering 0.1% of the conductor length and at current ramp rates as high as 2000 A s −1 . Voltage measurements thus remain an effective option for quench detection in magnets wound with HTS conductors for which current sharing between tapes allows for operation within the flux flow regime.